I think it’s as you said though, 100mm BB’s and 170mm back ends are more trail friendly.

I’ve read this comment a few times but have never heard a convincing argument for why.

I really enjoyed riding my ICT with 4.8″ JJs last summer, for example. Is there a 4″ tyre that will be better? Most comments from people who have ridden the 4.0 and the 4.8 JJ suggest that they preferred the 4.8, but if there is a better tyre for summer fatbiking I’d be happt to give it a try.

Similarly, in the winter, is there a tyre that will cope better with wet roots, mud etc than the Bud/Lou combo I’ve got at the moment. Again, if there is I’d be happy to try it.

I’ve read this comment a few times but have never heard a convincing argument for why.

Because you feet/knees are an inch closer together.

And because for trail riding a rounded tyre does work better once lent over.

I don’t think there’s anything wrong with 5″ tyres, it’s just another step down the spectrum form normal (2″), plus(3″), 4″ to 5″. It’s just a question of how fat do you want to go and making a judgement, rather than just fatter = better. Would you ride a 6″ fat bike with a 140mm BB and 210mm rear end?

thisisnotaspoon – Member

Because you feet/knees are an inch closer together.

Well, no, not necessarily. In my 197 rear bike I’m using Raceface’s 170 rear cranks and they work perfectly with a 4.8 rear- albeit single ring only. I’m pretty sure with a 4.0 rear, double ring would work too.

The mech’s more exposed on 197 and naturally it’s a little heavier but it brings options, and choice is good.

But this is all getting a bit off the point which is that 170QR is a legacy standard and was the wrong choice for a new frame outside of the bargain basement. Nothing wrong with 170 in itself.

thisisnotaspoon – Member

And because for trail riding a rounded tyre does work better once lent over.

I don’t think that’s true. Certainly isn’t in normal bikes. But besides, a 4.8 and 4.0 in an 80mm rim can have pretty similar profiles. There’s no major difference between my 4.0 and 4.88 JJ in shape. Just depends how the tyre is designed.

I can see the market normalising around 150×15 front and 197×12 rears on the basis that frames can be built to accept the biggest available tyres – Snowshoe 2XLs and there’s no real need for anything bigger except for extreme winter riding. The likely demand for anything bigger is probably restricted to a few hundred riders only for events like the ITI – so not really worth the investment.

The trouble is that there are so many standards in the market and its such a small market. There’s economies of scale to consider and a spread of frames that take the same parts helps with stock management. In an ideal world we’d be able to shoehorn 197×12 rears onto a 83mm BB for a nice low Q factor and still let people run 5″s.

The Inbreds are due a refresh, thats on the table currently and we’re looking at the whole Fat Bike offering in a similar light. They’ve been good to us, and niches is where On-One really does well.

Let’s see what comes out in the wash over the next few weeks. We just want to make bike that people want to ride.

The paint on the frames?

Because you feet/knees are an inch closer together.

Ah, yes, the q-factor issue. Fair enough. Personally I’ve had less knee pain (or at least no more) since getting the ICT. But then I do walk like a bow-legged duck, so maybe it’s more of an issue for people with more normal legs.

And because for trail riding a rounded tyre does work better once lent over.

Isn’t that more a factor of rim width? A 4.8″ tyre on a 75mm rim would presumably be at least as round as a 3.8″ tyre on the same rim.

But I’m not trying to pick a fight. I agree with you. Ride whatever works for you. But I’ve seen this comment about 4″ tyres being better for trail riding than 5″ ones so often that I’m tempted to try it. But then I think about what I like about my 5″ fatbike and one thing I’m not thinking is “I wish it were less fat”